Flotation concentration of magnesite with emulsified collector reagents

ABSTRACT

Concentration of magnesite present in ores containing siliceous and calcareous impurities and having some clay slimes as impurities by first reducing the slimes content of a magnesite ore pulp. cleaning same in a first flotation treatment wherein some of said impurities are separated as a float product, mixing a selected group of depressants for said siliceous and calcareous impurities in predetermined proportions in a liquid carrier, adding the premixed depressants to the cleaned pulp feed to a second flotation treatment at a predetermined rate, and stage adding an emulsifiable tall oil fatty acid collector reagent of low rosin content in starvation amounts at intervals in the progressive pulp flow through the second flotation treatment thereby floating a portion of the total magnesite content at each introduction stage.

United States Patent Jepsen Feb. 8, 1972 [54] FLOTATION CONCENTRATION OF MAGNESITE WITH EMULSIFIED COLLECTOR REAGENTS [21] Appl.No.: 8,692

Related US. Application Data [63] Continuation-impart of Ser. No. 743,292, July 9,

1968, abandoned.

[52] US. Cl ..209/l2, 260/975, 209/166 [51] Int. Cl. ..B03b 7/00, 803d 1/02 [58] Field of Search ..209/166, 167, 3, 9,18, 12; 241/20; 252/85; 260/975 [56] References Cited UNITED STATESPATENTS 2,165,268 7/1939 Jorgensen ..209/ 166 2,302,338 11/1942 Moeller ..209/166 2,371,292 3/1945 Hoag ..209/166 X 2,744,888 5/1956 Carries ..260/97.5 2,831,574 4/1958 Weinig ....209/166 3,048,538 8/1962 Rosenberg. ...,.252/85 3,383,057 5/1968 Jepsen ..241/20 Primary Examiner-Frank W. Lutter Assistant Examiner-Robert Halper Attorney-McGrew and Edwards [57] ABSTRACT Concentration of magnesite present in ores containing siliceous and calcareous impurities and having some clay slimes as impurities by first reducing the slimes content of a magnesite ore pulp. cleaning same in a first flotation treatment wherein some of said impurities are separated as a float product, mixing a selected group of depressants for said siliceous and calcareous impurities in predetermined proportions in a liquid carrier, adding the premixed depressants to the cleaned pulp feed to a second flotation treatment at a predetermined rate, and stage adding an emulsifiable tall oil fatty acid collector reagent of low rosin content in starvation amounts at intervals in the progressive pulp flow through the second flotation treatment thereby floating a portion of the total magnesite content at each introduction stage.

7 Claims, No Drawings FLOTATION CONCENTRATION OF MAGNESITE WITH EMULSIFIED COLLECTOR REAGENTS This application is a continuation-in-part of application Ser. No. 743,292, filed July 9, 1968, now abandoned, for Flotation Concentration of Magnesite With Emulsified Collector Re agents.

The present invention relates to improvements in concentration of magnesite ore, particularly by treatments of the general character disclosed in my US. Pat. No. 3,383,057 of May 14, 1968 for Controlled Reagent Introduction in a Magnesite Ore Concentration Process, assigned to the assignee of the present invention.

Various procedures including froth flotation separations have been developed for concentrating magnesite ores to obtain a magnesite concentrate of adequate grade. The magnesite ores mined at Gabbs, Nye County, Nev. are representative of ores being treated in commercial operations to produce a concentrate suitable for use in the production of refractories. Such ores usually contain in addition to magnesium carbonate other minerals including dolomite, calcite tremolite, forsterite, brucite, hydromagnesite, serpentine, talc, pyrophyllite, chlorite, quartz, alumina compounds, clays, graphite and soluble salts, all of which are treated as impurities and must be substantially eliminated or reduced in quantity so as to yield a concentrate material suitable for use in the production of refractories.

Generally, the impurities are designated siliceous and calcareous impurities and the slirnes content usually comprising clays, graphite and the like in extremely fine sizes also is treated as an impurity. As the present process is intended to produce a high grade magnesite concentrate, it is necessary to eliminate a major portion of the siliceous and calcareous impurities to provide the desired grade, and prior to removal of such it is desirable to effect removal of a substantial portion of the slirnes in order to reduce the amount of collector reagent introduced into the treatment without impairing efficiency of the flotation separation.

One of the innovations of the procedure described and claimed in US. Pat. No. 3,383,057 is the utilization of a novel group of depressant agents for the siliceous and calcareous content of magnesite ore formed as a single solution which could be introduced by one reagent feeder. Another innovation in the procedure is the utilization of Portland cement, stabilized dolomite and hydraulic lime as a depressant. In such practice, the cement is introduced into the final grinding stage in established proportions and a thorough dispersion of the cement in the pulp results from the intense agitation and circulation of the grinding stage. The recommended procedure is to add cement in an amount between 2 and pounds per ton of ore milled.

in the preferred practice of the patented process, the ore taken for treatment is subjected to preliminary crushing to a half inch size or smaller, after which soluble salts and primary slimes, particularly clays, are removed by cyclone separation with the underflow of such separation passing through a second cyclone separation stage operating in closed circuit with a cement feeder and ball mill. This treatment and separation effects the size reduction to approximately minus 200 mesh and the sized ore is pulped to about 35 percent solids, conditioned and introduced into a first flotation stage at a temperature over 90 F. This flotation separation removes a substantial part of the siliceous and calcareous impurities which are passed to waste and any slimes fraction which is not wasted by the cyclone separation also passes with the reject concentrate material to waste.

The nonfloated residue of the first flotation separation stage is passed into a conditioning stage wherein the depressant agents are mixed preparatory to subjecting such nonfloated solids to a second flotation treatment which involves a plurality of stages in both rougher and cleaner circuits. The preferred practice of the present invention involves utilization of a flow sheet essentially the same as that shown and described in US. Pat. No. 3,383,057. As mentioned in said patent, tall oils comprise a satisfactory substitute material for the preferred oleic acid of that treatment, particularly when the rosin content of the tall oil reagent is low. Under the practice previously known, the tall oil reagent was substantially insoluble in water and therefore difficult to disperse within the pulp. Also, the tall oil collector tended to increase in concentration in the progression of pulp through a plurality of cells with stage addition of collector reagent, frequently resulting in flotation of some of the dolomite content with consequent reduction in grade of the final concentrate material.

Accordingly, it is an object of this invention to provide emulsified tall oil collector reagents of low rosin content for use in the flotation concentration of the magnesite content of magnesite ore pulps which produce a relatively high grade concentrate at low reagent cost.

Another object of my invention is to provide a group of emulsifiable tall oil collector reagents for magnesite ore concentration in which the emulsifiers are nonionic surfactants that effectively disperse the tall oil as colloidal particles in the water of an aqueous pulp so that such particles are more readily and more efficiently brought in contact with the grains of magnesite in the pulp under treatment.

A further object of the invention is to provide an efficient and economical flotation treatment of magnesite ore by the use of emulsifiable tall oil fatty acid collector reagents in conjunction with depressant reagents for the siliceous and calcareous impurities of the ore.

My investigation of the advantages derived from the use of an emulsifiable tall oil collector reagent in the flotation concentration of the magnesite content of magnesite ores has established that the emulsifiable collectors may be formed in a variety of ways and by mixing of materials of difierent chemical composition. In general, the desired type of emulsifiable collector reagent is formed by mixing a tall oil acid of low rosin content with a nonionic surfactant composition and preferably the latter is a condensation product of nonylphenol with ethylene oxide. The surfactant addition to the tall oil acid may be within the range of 5-15 percent by weight and generally best results will be attained if a 10 percent addition is used. Surfactants sold commercially and effective for use in the present treatment are Dowfax 9N9," a condensation product of nonylphenol and ethylene oxide of the following Tergitol NPX," a nonionic condensation product of nonylphenol and ethylene oxide, Triton N-lOl," a condensation product of nonylphenol and ethylene oxide, Emulphor EL-620," a nonionic product of the condensation of ethylene oxide with a fatty acid, and Gafamide CD-l 15, a condensation product of coconut fatty acid and diethanolamine. The tall oil and the surfactant may be added as a mixture or in separate streams from different reagent feeders, if desired.

Having described the nature of the ores treated by the present invention and cited a typical flow sheet for performing a preferred treatment, a typical example of comparative testing will be described. The procedure involved comparative tests using the same ore, procedure and reagents with the exception that in the first test no surfactant was added to the tall oil collector and in the second test a 10 percent addition of Dowfax 9N9 was used to form an emulsion. In these two tests the ore was prepared exactly as described in US. Pat. No. 3,383,057 by crushing, desliming and grinding to pass a 200- mesh screen with the addition of cement to the grinding circuit. Following such ore preparation, siliceous and calcareous impurities were removed in a first flotation treatment employing an amine collector reagent for such impurities, leaving substantially all the magnesite content of the ore charge as a nonfloated residue of the flotation separation. This nonfloated residue was passed into a conditioning stage with its solids content conditioned with a mixture of sodium hexametaphosphate, sodium silicate and aluminum sulfate dis- Tall oil fatty ncid without Tnll oll fatty acid with Dowfnx 9N0 10'7; Dowfnx 9N9 Percent Percent Percent Percent Percent Percent wt. ins. Ca wt. ins. C110 Based on said comparative tests and other similar testing and observation, I have found that the addition of a nonionic reagent such as Dowfax 9N9 has the advantage of rendering the tall oil fatty acid emulsifiable so that upon introduction as the collector reagent of the second flotation treatment the tall oil is dispersed as colloidal particles into the water of the aqueous pulp, which particles are more readily and more efiiciently brought in contact with the grains of magnesite. This more efficient contact results in more complete use of the fatty acid content at each introduction stage and lessens the possibility for progressive accumulation of substantial amounts of collector in the pulp which otherwise may induce dolomite flotation in later stages because of the increased concentration in the pulp. Also, an important economy is obtained by requiring lesser collector for the total flotation in the second flotation treatment and maintaining desired grade of concentrate.

Additional benefit to the treatment results from the selection of tall oil reagents of low rosin content. A series of comparative tests were undertaken using similar feed charges taken from the same ore source. Oleic acid was used as reagent in Test 1 designated without rosin, Test 2 had a 4 percent by weight addition of rosin to the oleic acid and Test 3 had a 20 percent addition. From this testing, I have established that a rosin content range of from to 5 percent by weight will provide a reagent capable of producing a concentrate of good grade with relatively high recovery. Such range is the low rosin content as used in this specification. The test results follow:

minimum required to impregnate or coat magnesite surfaces sufficiently to promote flotation of most or all of the magnesite content of the pulp. Whatever part of the total magnesite content which receives inadequate coating or impregnation at the early stages will receive sufficient coating or impregnation in a later stage and this procedure effectively floats most or all of the magnesite before final pulp discharge from the multistage flotation treatment. Due to the action of the depressants in preventing flotation of siliceous or calcareous impurities and the limited quantity of collector present in any flotation stage, a high-grade concentrate is obtained.

lclaim:

1. In a froth flotation treatment of magnesite ore, including introducing a pulp of magnesite ore in a flotation size range into a froth flotation separation, and introducing collector and depressant reagents into the pulp of the froth flotation separation, the improvement which comprises introducing increments of a tall oil fatty acid collector reagent of low rosin content rendcred emulsifiable by a nonionic surfactant into the pulp subjected to froth flotation at a plurality of stages, the total quantity of said collector so introduced being sufficient to float substantially the entire magnesite content of the pulp introduced into said separation.

2. A treatment as defined in claim 1, in which the ore charge taken for treatment is first subjected to a slirnes removal treatment, the ore so cleaned is conditioned with depre$ant reagents for the siliceous and calcareous impurities, and then subjected to the froth flotation at a plurality of stages with the increments of the emulsifiable tall oil fatty acid collector reagent introduced in starvation amounts to said plurality of stages.

3. A treatment as defined in claim 1, in which the tall oil collector reagent is rendered emulsifiable by a nonionic surfactant by mixing the tall oil collector reagent with a nonionic surfactant composition.

4. A treatment as defined in claim 1, in which said collector reagent is fed in starvation amounts to said plurality of stages.

5. A treatment as defined in claim 3, in which the collector reagent rendered emulsifiable by a nonionic surfactant is the product of mixing a tall oil acid of low rosin content in the range of 0-5 percent by weight with a 5-15 percent by weight addition of a nonionic surfactant composition.

6. A treatment as defined in claim 4, in which the quantity of collector reagent introduced into the plurality of stages is sufficient to float a high-grade magnesite concentrate at each stage.

7. A treatment as defined in claim 3, in which the surfactant Without rosin 4% rosin 20% rosin Percent Percent Percent Percent Percent Percent Percent Percent Percent insoi. CaO rec. insol. CaO ree. insol. CaO rec.

Heads 2. 27 4. 00 100.00 2. 27 4. 00 100.00 2. 27 4. 00 100. O0 6. 20 9. 35.04 4.95 9. 10 39. 01 3. 67 6. 80 54. 33 0. 1. 20 64. 96 0. 1. 30 60. 99 0. 75 1. 40 45. 67

Starvation amounts as used in this specification designates a quantity of reagent substantially less than the 

2. A treatment as defined in claim 1, in which the ore charge taken for treatment is first subjected to a slimes removal treatment, the ore so cleaned is conditioned with depressant reagents for the siliceous and calcareous impurities, and then subjected to the froth flotation at a plurality of stages with the increments of the emulsifiable tall oil fatty acid collector reagent introduced in starvation amounts to said plurality of stages.
 3. A treatment as defined in claim 1, in which the tall oil collector reagent is rendered emulsifiable by a nonionic surfactant by mixing the tall oil collector reagent with a nonionic surfactant composition.
 4. A treatment as defined in claim 1, in which said collector reagent is fed in starvation amounts to said plurality of stages.
 5. A treatment as defined in claim 3, in which the collector reagent rendered emulsifiable by a nonionic surfactant is the product of mixing a tall oil acid of low rosin content in the range of 0-5 percent by weight with a 5-15 percent by weight addition of a nonionic surfactant composition.
 6. A treatment as defined in claim 4, in which the quantity of collector reagent introduced into the plurality of stages is sufficient to float a high-grade magnesite concentrate at each stage.
 7. A treatment as defined in claim 3, in which the surfactant composition is a condensation product of nonylphenol with ethylene oxide. 